Electron tube circuits



Jan. 9, 1934. Q w 1 sElBERT 1,942,983

ELECTRON TUBE CIRCUITS Filed July 1 To Pen en JUPPLV we roe W/L 1. l4 4 65/55 7" Patented Jan. 9, 1934 STATES ELECTRON TUBE CIRCUITS William L. Scibert, Fort Monmouth, N. J.

Application July 10, 1930. Serial No. 467,028

9 Claims.

(Granted under the act of March 3, 1883, as

amended April 30, 1928; 370 0. G. 757) ihe invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon.

This invention relates to electron tube circuits, and more particularly to the circuits used in electron tube radio transmitting sets.

One of the objects of my invention is to provide a convenient output circuit for power amplifiers which will prevent overheating of tubes when the output circuit is detuned.

A further object is to reduce the harmonic component frequencies generated in vacuum tube circuits, which usually are not utilized, thereby reducing the necessary plate power supply and plate dissipation to substantially that required for the operating frequency only.

A still further object is to reduce the amplitude of the harmonic component frequencies radiated by a radio transmitter and the consequent unnecessary interference set up at these higher frequencies.

A clear understanding of the invention may be had by reference to the following description of a complete embodiment which is illustrated in the accompanying drawing. In this drawing is shown a diagram of the output tank circuit of an electron tube amplifier.

Referring now to the drawing, an electron tube, as a radio frequency amplifier, is represented at 1. The plate of the electron tube is connected to a radio frequency choke coil 2, and from this choke to a tuned tank circuit 3 which connects, turn, to the D. C. plate power supply.

The choke coil 2 may be designed to be nearly resonant at the operating frequency. The choke 2 and tuned tank circuit 3 then provide series resonance in the plate circuit so that the plate current is at a low value with the tank circuit detuned, and the plate current reaches its maximum for the same, or nearly the same, tuning setting of the tank circuit which produces maximum circulating current in the tank circuit. The choke reactance is then inductive when the tank circuit is capacitive, and vice versa. This eliminates any tendency of the tube to overheat due to the excessive plate current ordinarily obtained when the load or tank circuit is detuned. This characteristic operation extends over a considerable frequency band on each side of the resonant frequency of the choke. An arrow is shown in. the diagram to indicate that the connection to the tank circuit may be made at some point other than the. free end. if this is found to be advisable in order to match better the load and tube impedances.

The choke coil, previously mentioned, consists of a winding of wire having'inductance and distributed capacity which, together, determine the resonant or natural frequency of the choke. At this frequency the choke offers highreactance or impedance, due to parallel resonance, to the alternating current passing thru it. For. the operating frequency, this is compensated by a similar reactance l8fi out of phase in the tuned tank circuit. The choke coil also offers similar high impedance to all odd harmonic components of the operating alternating current. As the impedance of the tuned tank circuit is low at all harmonic frequencies, the series plate resonance phenomena experienced by the operating frequency will not be shared by the harmonics. This causes the odd harmonic components to be limited effectually. As an elaboration of this means of limiting harmonics, choke coils resonant at twice and three times, or more, the operating frequency may be inserted in series with the plate in order to reduce the harmonic components at which they are effective.

The embodiment consisting of the output circuit of an electron tube amplifier was chosen because it is a complete demonstration of the objects attained by this invention. Another valuable application is the use of similar chokes in the plate lead of electron tube oscillators, the chokes being parallel resonant at harmonic frequencies in order to reduce the amplitude of these components.

While I have described certain forms of my invention in detail, and while I have pointed out certain of the most obvious principles and purposes thereof, 1 do not intend that the langauge employed in the following claims shall be limited to the precise features described, but I intend that the claims shall be construed to cover all combinations which are fairly included in the language thereof, when read in view of the prior art regardless of the details and functions menincluding an electron tube having a plate circuit; a tuned load circuit operatively associated with said plate circuit; and a choke coil in series with said circuit, said coil having high impedance at the operating frequency.

3. An electron tube power amplifier circuit, including an electron tube having a plate circuit; a tuned load circuit operative with the said plate circuit; and a choke coil in series with said circuits, said coil having high impedance at the operating frequency and harmonic component frequencies.

4. An electron tube circuit, including an electron tube having a plate circuit; and a choke coil in said circuit, said coilhaving distributed inductance and capacitance Whose relative values are such as to provide large reactance at har monic frequencies of the operating frequency and functioning to reduce the power dissipated at the plate by certain harmonic components of the operating frequency.

5. An electron tube circuit and a choke coil included in said circuit, said coil having distributed inductance of relatively large value and distributed capacitance of relatively low value and functioning to reduce the amplitude of various harmonic components of the operating frequency.

6. An alternating current circuit and a tuned output circuit operatively associated therewith;

and a choke coil in series with said output circuit, the said coil having high impedance at the operating frequency and harmonic component frequencies.

7. An alternating current circuit, including an electron tube having a plate circuit; a tuned output circuit associated with said plate circuit; and a choke coil in series with the plate circuit and output circuit, said coil having high impedance at the operating frequency and harmonic component frequencies.

8. An alternating current circuit and a load circuit operatively associated therewith; and a choke coil in series with the load circuit, said coil having high impedance at the operating frequency and harmonic component frequencies.

9. In an electron tube amplifier circuit, including an electron tube having a plate circuit; a tuned output circuit operatively associated with the plate circuit; and a choke coil iutercalated in series between said plate and output circuits, saicl coil acting in cooperation with the output circult to provide series resonance in said plate circuit when said output circuit is tuned to the operating frequency, and having distributed inductance and distributed capacitance whose relative values are such as to reduce the plate current when said output circuit is detuned.

WILLIAM L. SEIBERT. 

